Conserving seasonal pans

Seasonal pans are found across Malilangwe, but they are most common on alluvial and basalt geology. The pans are inhabited by large branchiopod crustaceans, commonly known as fairy shrimps. Approximately 66 species have been recorded in southern Africa, but diversity may be higher because large areas, including parts of Zimbabwe, remain unstudied. Little is known about the influence of local geology and geomorphology on the diversity and distribution of branchiopods, so an investigative study was carried out at Malilangwe between 2009 and 2010 (Tuytens et al. 2015). The diversity of shrimps was sampled in 160 pans of variable size that were distributed across four geological types. Seven species of fairy shrimp and one tadpole shrimp were found. Surprisingly, there was no correlation between shrimp diversity and geological type.

An earlier study at Malilangwe had shown that the eggs of the shrimps are transported across the landscape by mud wallowing animals such as elephants, buffalo and rhino (Vanschoenwinkel et al. 2011). The eggs are carried in mud on the backs of these animals until it is rubbed off on trees and bushes. The mud is then washed off with the next rain and, with luck, the eggs are transported by surface flow into a nearby pan where they can start their life cycle once more. Elephants, rhinos and buffalo are capable of moving long distances, so considerable mixing of species across the landscape is possible. This may explain why there was no correlation between shrimp diversity and geological type. Studies such as these highlight the importance of biodiversity for the functioning of ecosystems. What would happen to the shrimps if there were no elephants, buffalos or rhinos, and what then would happen to the organisms that depend on the shrimps, and so on?